[Lustre-discuss] [PATCH] Avoid Lustre failure on temporary failure on create QP

[Alexey Lyashkov]

Eli,

We have a ticket may addressed to that change and you help to solve it. 
Thank you very much.

On Aug 31, 2014, at 11:53 AM, Eli Cohen <eli at dev.mellanox.co.il> wrote:

> Lustre code tries to create a QP with max_send_wr which depends on a module
> parameter.  The device capabilities do provide the maximum number of send work
> requests that the device supports but the actual number of work requests that
> can be supported in a specific case depends on other characteristics of the
> work queue, the transport type, etc. This is in compliance with the IB spec:
> 
> 11.2.1.2 QUERY HCA
> Description:
> Returns the attributes for the specified HCA.
> The maximum values defined in this section are guaranteed
> not-to-exceed values. It is possible for an implementation to allocate
> some HCA resources from the same space. In that case, the maximum
> values returned are not guaranteed for all of those resources
> simultaneously.
> 
> This patch tries to decrease the number of requested work requests to a level
> that can be supported by the HCA. This prevents unnecessary failures.
> 
> Signed-off-by: Eli Cohen <eli at mellanox.com>
> ---
> lnet/klnds/o2iblnd/o2iblnd.c | 25 ++++++++++++++++++-------
> 1 file changed, 18 insertions(+), 7 deletions(-)
> 
> diff --git a/lnet/klnds/o2iblnd/o2iblnd.c b/lnet/klnds/o2iblnd/o2iblnd.c
> index 4061db00cba2..ef1c6e07cb45 100644
> --- a/lnet/klnds/o2iblnd/o2iblnd.c
> +++ b/lnet/klnds/o2iblnd/o2iblnd.c
> @@ -736,6 +736,7 @@ kiblnd_create_conn(kib_peer_t *peer, struct rdma_cm_id *cmid,
> 	int			cpt;
> 	int			rc;
> 	int			i;
> +	int			orig_wr;
> 
> 	LASSERT(net != NULL);
> 	LASSERT(!in_interrupt());
> @@ -862,13 +863,23 @@ kiblnd_create_conn(kib_peer_t *peer, struct rdma_cm_id *cmid,
> 
> 	conn->ibc_sched = sched;
> 
> -        rc = rdma_create_qp(cmid, conn->ibc_hdev->ibh_pd, init_qp_attr);
> -        if (rc != 0) {
> -                CERROR("Can't create QP: %d, send_wr: %d, recv_wr: %d\n",
> -                       rc, init_qp_attr->cap.max_send_wr,
> -                       init_qp_attr->cap.max_recv_wr);
> -                goto failed_2;
> -        }
> +	orig_wr = init_qp_attr->cap.max_send_wr;
> +	do {
> +		rc = rdma_create_qp(cmid, conn->ibc_hdev->ibh_pd, init_qp_attr);
> +		if (!rc || init_qp_attr->cap.max_send_wr < 16)
> +			break;
> +
> +		init_qp_attr->cap.max_send_wr /= 2;
> +	} while (rc);
> +	if (rc != 0) {
> +		CERROR("Can't create QP: %d, send_wr: %d, recv_wr: %d\n",
> +		       rc, init_qp_attr->cap.max_send_wr,
> +		       init_qp_attr->cap.max_recv_wr);
> +		goto failed_2;
> +	}
> +	if (orig_wr != init_qp_attr->cap.max_send_wr)
> +		pr_info("original send wr %d, created with %d\n",
> +			orig_wr, init_qp_attr->cap.max_send_wr);
> 
>         LIBCFS_FREE(init_qp_attr, sizeof(*init_qp_attr));
> 
> -- 
> 2.1.0
> 
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